Registration Dossier

Administrative data

Endpoint:
carcinogenicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Study conducted in compliance with agreed protocols, with no deviations from standard test guidelines and no methodological deficiences, which do not affect the quality of the relevant results. The study report was conclusive, done to a valid guideline and the study was conducted under GLP conditions.

Data source

Reference
Reference Type:
study report
Title:
Unnamed

Materials and methods

Test guideline
Qualifier:
no guideline available
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Details on test material:
Allyl bromide was obtained from Fluka Chemical Corporation (Buchs, Switzerland) in one lot (330638) and from Aldrich Chemical Co. in one lot (03614HN). Lot 330638 was used in the 2-week studies, and lot 03614HN was used in the 40-week studies. Identity and purity analyses were conducted by the analytical chemistry laboratory, Midwest Research Institute (Kansas City, MO) and the study laboratory, BioReliance (Rockville, MD). Reports on analyses performed in support of the allyl bromide studies are on file at the National Institute of Environmental Health Sciences.
Both lots of allyl bromide, a clear, colorless liquid, were identified by the analytical chemistry laboratory using infrared and proton nuclear magnetic resonance (NMR) spectroscopy and by the study laboratory using infrared spectroscopy. All infrared and NMR spectra were consistent with the literature spectra and spectra of a reference standard from the same lot. The purity of each lot was determined by the analytical chemistry and study laboratories using gas chromatography (GC). For lot 330638, GC indicated one major peak and five impurities with a combined peak area of 0.7% relative to the total peak area. GC by a second system indicated one major peak and three impurities with a combined peak area of less than 0.5%. The relative purity was 102% when compared to a reference standard from the same lot. The overall purity of lot 330638 was greater than 99%. For lot 03614HN, GC indicated one major peak and four impurities with a combined peak area of 0.45% relative to the total peak area. GC by a second system indicated one major peak and three impurities with a total combined area less than 0.3% of the total peak area. The relative purity was 102% when compared to a frozen reference from the same lot. The overall purity of lot 03614HN was greater than 99%. During the 40-week studies, additional purity analyses were performed by the study laboratory at 26 weeks and at the end of the study using GC.
To ensure stability, the bulk chemical was stored in a sealed container under a nitrogen headspace, protected from light, at 2° to 8° C. No degradation of the bulk chemical was detected.

Test animals

Species:
mouse
Strain:
other: FVB/N - C57BL/6 - Tg.AC hemizygous- p53 haploinsufficient mice
Sex:
male/female
Details on test animals and environmental conditions:
Source and Specification of Animals
Male and female FVB/N, C57BL/6, Tg.AC hemizygous, and p53 haploinsufficient mice were obtained from Taconic Farms, Inc. (Germantown, NY), for use in the 2-week and 40-week studies. FVB/N and C57BL/6 mice were quarantined for 14 or 15 days, respectively, before the beginning of the 2-week studies. FVB/N and Tg.AC hemizygous mice were quarantined for 11 or 12 days and C57BL/6 and p53 haploinsufficient mice were quarantined for 12 days before the beginning of the 40-week studies. Before the 2-week and 40-week studies, five male and five female mice per strain were randomly selected for parasite evaluations and gross observations of disease. FVB/N and C57BL/6 mice were 7 or 8 weeks old, respectively, at the beginning of the 2-week studies. FVB/N, Tg.AC hemizygous, C57BL/6, and p53 haploinsufficient mice were 7, 6, 9, and 9 weeks old, respectively, at the beginning of the 40-week studies. At the end of the 40-week studies, blood samples were collected from the retroorbital sinus of five male and five female vehicle control mice per strain. The sera were analyzed for antibody titers to rodent viruses (Boorman et al., 1986; Rao et al., 1989a,b). All results were negative.

Animal Maintenance
Mice were housed individually. Feed and water were available ad libitum. Cages and racks were rotated every other week during the 40-week studies.

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
corn oil
Details on exposure:
40-Week Gavage Studies
Groups of 15 male and 15 female FVB/N and C57BL/6 mice received 0 or 8 mg allyl bromide/kg body weight in corn oil by gavage, in a volume of 10 mL/kg body weight, 5 days per week for 40 weeks. Groups of 15 male and 15 female Tg.AC hemizygous and p53 haploinsufficient mice received 0, 0.5, 1, 2, 4, or 8 mg allyl bromide/kg body weight in 10 mL/kg corn oil by gavage, 5 days per week for 40 weeks. Vehicle control mice received corn oil only.
Duration of treatment / exposure:
40 weeks
Frequency of treatment:
5 days per week for 40 weeks
Post exposure period:
None
No. of animals per sex per dose:
15 male and 15 female mice
Control animals:
yes, concurrent vehicle
Positive control:
Positive Control Mice
Positive control groups of 15 male and 15 female Tg.AC hemizygous mice received dermal applications of 1.25 μg TPA in 100 μL acetone (12.5 μg TPA/L solution), three times per week until removal from study. Positive control mice were removed after the appearance of 20 or more skin papillomas and discarded. The TPA solution was applied to the clipped dorsal skin from the mid-back to the interscapular area.

Results and discussion

Results of examinations

Body weight and weight changes:
no effects observed
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
Appendix A to D of the report
Histopathological findings: neoplastic:
effects observed, treatment-related
Description (incidence and severity):
Appendix A to D of the report
Details on results:
40-Week Gavage Study in FVB/N Mice
Survival
Estimates of 40-week survival probabilities for male and female mice are shown in Table 5. Survival of dosed male and female mice was similar to that of the vehicle control groups. One male and one female administered 8 mg/kg died before the end of the study.

Body Weights, Clinical Findings, and Organ Weights
Mean body weights of dosed male mice were generally similar to those of vehicle controls, and those of dosed female mice were generally greater throughout the study. There were no treatment-related clinical findings. Organ weights of 8 mg/kg males and females were similar to those of the vehicle control groups.

Pathology and Statistical Analyses
There were no statistically or biologically significant increases in neoplasms or nonneoplastic lesions in FVB/N mice administered allyl bromide by gavage for 40 weeks. Summaries of the incidences of neoplasms and nonneoplastic lesions are presented in Appendix A for male and female FVB/N mice. Three (20%) dosed males (8 mg/kg), two (13%) vehicle control females, and one (7%) dosed female (8 mg/kg) developed alveolar/bronchiolar adenomas. Mahler et al. (1996) reported spontaneous alveolar/bronchiolar adenoma rates in 14-month-old FVB/N mice of 2/45 (4%) for males and 8/98 (8%) for females. Mice in the current study were approximately 11 months old at the end of the study.

40-Week Gavage Study in Tg.AC Hemizygous Mice
Positive Control Tg.AC Hemizygous Mice
12-O-Tetradecanoylphorbol-13-acetate (1.25 μg) was dermally administered to groups of 15 male and 15 female mice. Except for one female that died early, all males and females developed more than 20 skin papillomas each by week 18. This is consistent with historical rates found in other studies and indicates that the Tg.AC mice in this entire study were of the “responder” genotype (Tennant et al., 2001).

Survival
Estimates of 40-week survival probabilities for male and female mice are shown in Table 8. Survival of dosed mice was similar to that of the vehicle control groups.

Body Weights, Clinical Findings, and Organ Weights
Mean body weights of dosed mice were generally similar to those of the vehicle control mice throughout the study. There were no treatment-related clinical findings in male mice. In female mice, there were increased numbers of cutaneous and mucocutaneous masses (gross observations) on the body, particularly the vaginal and vulvar area, and these papillomas were observed earlier in the dosed groups. There were no biologically significant differences in organ weights of dosed groups compared to the vehicle control groups.

Pathology and Statistical Analyses
This section describes the statistically significant or biologically noteworthy changes in the incidences of neoplasms of the skin. Summaries of the incidences of neoplasms and nonneoplastic lesions are presented in Appendix B for male and female Tg.AC hemi-
zygous mice.
Skin: The incidences of squamous cell papilloma of the vulva increased with a positive trend (P=0.018). The incidences of squamous cell papilloma at all skin sites (including vulva) also increased with a positive trend (P<0.05). Squamous cell papillomas of the vulva tended to be larger in treated mice (1 to 7 mm in greatest diameter; average diameter was 2.3 mm) than those in control mice (1 mm or less in greatest diameter). Size of papillomas did not seem to increase with increasing dose.

40-Week Gavage Study in C57BL/6 Mice
Survival
Estimates of 40-week survival probabilities for male and female mice are shown. Survival of dosed mice was similar to that of the vehicle control groups, although three 8 mg/kg females died early.

Body Weights, Clinical Findings, and Organ Weights
Mean body weights were similar between dosed and vehicle control mice. There were no treatment-related clinical findings. There were
no statistically significant differences in organ weights between the dosed and vehicle control groups.

Pathology and Statistical Analyses
There were no chemical-related gross or microscopic findings in C57BL/6 mice administered allyl bromide for 40 weeks. Summaries of the incidences of neoplasms and nonneoplastic lesions are presented for male and female C57BL/6 mice.

40-Week Gavage Study in p53 Haploinsufffficient Mice
Survival
Estimates of 40-week survival probabilities for male and female mice are shown . Survival of dosed male and female mice was similar to that of the vehicle controls with no more than two deaths per group.

Body Weights, Clinical Findings, and Organ Weights
Mean body weights of 0.5, 4, and 8 mg/kg males were marginally greater than those of the vehicle controls after week 9 of the study. Mean body weights of 8 mg/kg females were marginally greater than those of the vehicle controls after week 10, and those of 4 mg/kg females were generally less after week 21. There were no treatment-related clinical findings. Relative kidney and heart weights of females administered 4 mg/kg were significantly greater than those of the vehicle control group.

Pathology and Statistical Analyses
There were no chemical-related gross or microscopic findings in p53 haploinsufficient mice administered allyl bromide for 40 weeks. Summaries of the incidences of neoplasms and nonneoplastic lesions are presented for male and female p53 haploinsufficient mice.

Applicant's summary and conclusion

Conclusions:
In the 40-week study conducted in Tg.AC mice, the increase in total skin papillomas and vulvar tumors in female mice was significant by the Cochran-Armitage trend statistic. One hypothesis for this effect is the formation of a reactive metabolite derived from allyl mercapturic acid sulfoxide that was excreted in the urine, was absorbed by surrounding tissue (such as vulvar cells), and caused DNA damage (Kaye et al., 1972; Schuphan and Casida, 1979a,b). There were no treatment-related lesions in the forestomach.
There were no significant allyl bromide treatment-related increases in tumors in the other mice studied (FVB/N, C57BL/6, and p53 haploinsufficient mice). Studies of the allyl bromide metabolite acrolein also showed no evidence for a carcinogenic effect in rats or mice. A study on the potential of acrolein to cause cancer in CD-1 mice receiving 0, 0.5, 2, or 4.5 mg/kg per day by gavage for 18 months showed no evidence, nor did an acrolein study in Sprague-Dawley rats receiving 0, 0.05, 0.5, or 2.5 mg/kg per day by gavage for 18 months (Parent et al., 1991, 1992). No acrolein-induced cancers were seen when the chemical was administered in the drinking water to F344/N rats for up to 2 years (Linjinsky and Reuber, 1987; Linjinsky, 1988).

Under the conditions of this study, there was no evidence of carcinogenic activity in male or female p53 haploinsufficient mice administered allyl bromide at 0.5, 1, 2, 4, or 8 mg/kg per day by corn oil gavage, 5 days a week for 40 weeks.
There was a marginal increase in the incidence of squamous cell papillomas, primarily of the vulva, in female Tg.AC hemizygous mice administered allyl bromide by corn oil gavage for 40 weeks. No treatment-related neoplasms were seen in male Tg.AC hemizygous mice administered allyl bromide by gavage at 0.5, 1, 2, 4, or 8 mg/kg, 5 days per week for 40 weeks.
Executive summary:

40-Week Study in FVB/N Mice

Groups of 15 male and 15 female FVB/N mice were administered 0 or 8 mg allyl bromide/kg body weight in corn oil by gavage, 5 days a week for 40 weeks. Survival of dosed mice was similar to that of the vehicle controls. Mean body weights of dosed mice were within 10% of those of the vehicle controls throughout most of the study. There were no chemical-related gross or microscopic findings in dosed mice.

40-Week Study in Tg.AC Hemizygous Mice

Groups of 15 male and 15 female Tg.AC hemizygous mice were administered 0, 0.5, 1, 2, 4, or 8 mg allyl bromide/kg body weight in corn oil by gavage, 5 days a week for 40 weeks. Survival of dosed mice was similar to that of the vehicle controls. Mean body weights were generally similar between dosed and vehicle control mice throughout the study. In female mice, there were increased numbers of cutaneous and mucocutaneous masses (gross observations) on the body, particularly the vaginal and vulvar area, and these papillomas were observed earlier in the dosed groups. There were positive trends in the incidences of squamous cell papilloma of the vulva and of all skin sites in females.

40-Week Study in C57BL/6 Mice

Groups of 15 male and 15 female C57BL/6 mice were administered 0 or 8 mg allyl bromide/kg body weight in corn oil by gavage, 5 days a week for 40 weeks. Survival of dosed mice was similar to that of the vehicle controls. Mean body weights and organ weights were similar between dosed and vehicle control mice throughout the study. There were no chemical-related gross or microscopic findings in dosed mice.

40-Week Study in p53 Haploinsufffficient Mice

Groups of 15 male and 15 female p53 haploinsufficient mice were administered 0, 0.5, 1, 2, 4, or 8 mg allyl bromide/kg body weight in corn oil by gavage, 5 days a week for 40 weeks. Survival of dosed mice was similar to that of the vehicle controls. Mean body weights of dosed mice were within 10% of those of the vehicle controls throughout most of the study. Mean body weights of 8 mg/kg females were 11% to 15% greater than those of the vehicle controls from week 26 to week 33, and those of 4 mg/kg females were generally less after week 21. There were no chemical-related gross or microscopic findings.